IS CANNABIS A RISK TO HEALTH?

The decision to downgrade cannabis was always going to be
controversial.

After all, the jury is still out on the long-term effects of smoking a
joint.

There is strong evidence to suggest that smoking cannabis can harm
physical health.

CAN IT TRIGGER DEPRESSION?

Smoking regularly - regardless of whether it is tobacco or cannabis - can
increase the chances of developing lung cancer and other diseases.

However, research published two years ago suggested smoking cannabis
may be more harmful than cigarettes.

Cancer concerns

Tar in cannabis cigarettes can contain as much as 50% more
cancer-causing carcinogens than tobacco.

What's more, cannabis smokers tend to draw more heavily on joints than
cigarette smokers - increasing their risk of cancer further.

The government scientists who recommended the reclassification of
cannabis described the risk as "real".

In their report, the Advisory Council on the Misuse of Drugs said
smoking cannabis can increase the risk of "bronchitis, asthma and lung
cancer as well as disorders of the heart and circulation".

This is one of the reasons why if the UK government allows the use of
cannabis for medicinal purposes, it will come in pill form and will
only contain the active ingredients of the drug.

While the risks to physical health are relatively clear cut, there is
a debate about the impact of cannabis on mental health.

Some experts believe that smoking cannabis can trigger a range of
mental health problems, from depression to psychoses.

However, others disagree saying there is only a risk for those people
who are already ill.

In its report, the advisory council, which includes some of Britain's
top medical and scientific minds, said "no clear causal link has been
demonstrated" to show cannabis can lead to mental health problems.

However, it acknowledged that "acute cannabis intoxication" or being
stoned can lead to "panic attacks, paranoia and confused feelings".

The experts also warned that cannabis can "produce a psychotic state
that may continue for some time and may require treatment with
antipsychotic drugs".

When it came to people with mental illness, they were even more
robust.

"Cannabis use can unquestionably worsen schizophrenia and other mental
illnesses and lead to relapse in some patients," they said.

Nevertheless, the council insisted that cannabis should be
reclassified.

Until now, cannabis has been classed alongside drugs like
amphetamines. It will now be grouped alongside steroids and
tranquilisers.

The advisors were worried that keeping cannabis in Class B ran the
risk of cannabis users thinking "that if they have no harmful effects
from cannabis then other Class B substances will be equally safe".

'Wrong message'

However, other experts are concerned the move sends out the wrong
message to the public.

Cliff Prior, chief executive of the mental health charity Rethink, is
against it.

"People hear that cannabis is no longer a serious drug, that the
police won't make arrests except in the most serious circumstances and
that government is willing to downgrade it. People hear the message
that cannabis is risk-free."

Dr Peter Maguire of the British Medical Association shares that
view.

"The BMA is extremely concerned that the public might think that
reclassification equals 'safe'. It does not."

Professor Robin Murray, one of the country's top psychiatrists, says
there is growing evidence that people who regularly smoke cannabis are
putting themselves at risk.

"We and about five other studies in other countries have shown that if
you start taking cannabis early and heavily - say you're taking
cannabis daily by age 18 - then you are about seven times more likely
to develop schizophrenia than the rest of the population.

"You have to keep taking a lot every day to develop that sort of risk
but psychiatric units like mine are full of people who would not have
gone psychotic, who would not have developed schizophrenia, if they
did not smoke cannabis."

Professor John Henry, a toxicologist at St Mary's Hospital in
Paddington, grabbed headlines last year when he warned about the risks
of smoking cannabis.

Addressing a conference in London, he said he was convinced the drug
can cause mental illness.

"Regular cannabis smokers develop mental illness. There's a four-fold
increase in schizophrenia and a four-fold increase in major
depression," he said.

'Not as harmful'

However, others have yet to be convinced. Frank Warburton, acting
chief executive of DrugScope, supports the decision to downgrade cannabis.

"Cannabis is not as harmful as other Class B drugs," he
says.

"While we agree that there may be link between cannabis and mental
illness, we would argue against the simple assumption that cannabis
causes mental illness.

"If someone had a pre-existing condition, then cannabis may exacerbate
it. That is not the same as saying cannabis causes mental illness."

Mark, who first used cannabis when he was 12, said he backed the
decision to downgrade cannabis.

"Cannabis is nothing. It doesn't cause any problems. It doesn't cause
any violence.

"People don't have to go out and break the law to fund it. It is cheap
to buy. I don't think this will cause any problems."